The present invention concerns a new resin compound, and more specifically, it concerns a resin compound which has superior electrical conductivity, blackness, lubricating characteristics, etc., and which is made of a synthetic resin and ultra-fine carbon fibrils with special structures.
Information processing and office automation equipment is quickly becoming popular in recent years due to the rapid development in electronics technology. As such electronics equipment becomes more popular, electro-magnetic problems caused by the noises generated by the electronic parts on their peripherals, or operating troubles caused by static electricity have become a serious issue. Materials with superior electrical conductivity or electrical insulating characteristics are in great demand in these areas for the purpose of solving these problems.
Conventionally, electro-conductive polymers have been widely used which are produced by imparting electrical conductivity to polymer materials with poor electrical conductivity through the addition of an electro-conductive filler. Metal fibers, metal powder, carbon black, carbon fibers, etc. are generally used as an electro-conductive filler. However, metal fibers and metal powder, when used as an electro-conductive filler, have shortcomings such as poor corrosion resistance or difficulty in obtaining sufficient mechanical strength despite their excellent electrical conductivity.
When using carbon black as an electro-conductive filler, special electro-conductive carbon black such as Kechen Black, Vulcan XC72, or acetylene black are normally used instead of normal carbon black. However, such special carbon black does not easily disperse in resin material. Since dispersion of carbon black significantly affects the electrical conductivity of the product resin compound, special compounding and mixing techniques are required in order to obtain stable electrical conductivity.
On the other hand, when carbon fiber is used as an electro-conductive filler, desired strength and elasticity can be obtained by using the normal carbon fiber. However, a high filler content is required in order to impart electrical conductivity, resulting in the deterioration of the original characteristics specific to the resin itself. Further, if a molded product with a complicated shape is intended, uneven filler distribution tends to occur, which in turn results in uneven electrical conductivity. In the case of carbon fiber, a greater electrical conductivity imparting effect is expected when the fiber diameter is smaller, resulting in a greater contact area between the resin body and the fiber.
As an example of such fine carbon fibers, ultra-fine carbon fibrils with superior electrical conductivity have been described in Early Disclosure Patent Gazette Sho 62-500943. However, this carbon fibril is still unsatisfactory because when it is mixed with a resin, it is poorly distributed in the resin, substantially damaging the appearance of the molded product.
Furthermore, when carbon black is used merely for the purpose of coloring a resin, a relatively large amount of carbon black is required in order to obtain a desired blackness when conventionally known carbon black is used as a pigment (black pigment), which in turn causes problems with dispersion and appearance of the molded product.
The present invention intends to achieve a steadily high electrical conductivity and/or superior blackness without losing the molding ability and surface appearance of the resin compound by uniformly dispersing ultra-fine carbon fibrils in the process of imparting electrical conductivity and/or blackness to a resin.